The Sexy Anemone Shrimp (Thor
amboinensis de Man, 1888) is a distinctive orange coloured shrimp with a number of large white spots, ringed
in blue. The common name is coming from its unusual dance, which involves
holding its abdomen up in the air (like it just doesn’t care) and waving it all
around. This behaviour is done for camouflage or warning. It lives between
algae, sea grasses and sea anemone, gaining protection in the same manner as
Clownfish ... Photo by PADI Dive Instructor Ola Khalaf in the Kalba Sea on a
depth of 20 meters ... 31.03.2017… http://marine-life-uae.webs.com/sexy-shrimp

The Sexy or Squat
shrimp, Thor amboinensis is a small, spotted shrimp found in shallow
coral reef areas throughout Bermuda, the Caribbean and the Indo-Pacific
region. Thor amboinensis is one of the most common species of
shrimp seen throughout the Indo-Pacific, but is rarely seen in Bermuda or the
Caribbean. These shrimp are distributed with respect to available host
habitat. Thor amboinensis shares a symbiotic relationship with
several species of anemones by living within their tentacles. Some Squat shrimp
have even been observed providing cleaning service to Mantis shrimp, Lysiosquillina
lisa. Thor amboinensis is sometimes nicknamed the sexy
shrimp due to its tendency to vibrate its abdomen while walking. Even
though Thor amboinensis is a very commonly sold decapod in the
aquarium industry, it is still poorly understood (Ruzanski & Wood).

Thor
amboinensis is a small
shrimp growing to a length of about 13 millimeters (0.5 in). It is an
olive brown colour with symmetrically placed white patches edged with thin blue
lines. It characteristically carries its abdomen curved upwards with its tail
fan above its head (Wikipedia).

Thor amboinensis are usually
less than 1.3 cm in size (Boyer, 2002). Being a member of the Hippolytidae
family, these shrimp have short-stalked eyes that are not covered by their
carapace (Sterrer, 1986). The rostrum is well developed and does not overreach
the eyes or expand ventrally (Sterrer, 1986). Thor amboinensis are
a deep brown color with bright white splotches outlined in blue. The abdomens
and tails of these shrimp typically arch upwardly towards their heads (Boyer,
2002; Ruzanski &
Wood).

Habitat

Squat shrimp are
found on anemones in shallow waters throughout the Caribbean and Indo-Pacific.
These shrimp, although sparse are also located in Bermuda among inshore patch
reefs to the terrace reefs (Sterrer 1986). Thor amboinensis lives
protected from predators within an anemone’s tentacles which serve as protection
and food for the shrimp, while the host anemone is unaffected (Wirtz 1997,
Boyer 2002).
These shrimp are typically found in groups within a single anemone (Khan et. al.
2004). Within host anemones, Thor amboinensis feed primarily
on mucus-covered tentacles and on the planktonic organisms that are trapped
upon them (Guo et. al. 1996). Thor amboinensis has been found on
the Carpet anemone (Stichodactyla haddoni), Club tipped anemone (Telmatactis
cricoides), the Adhaesive anemone (Cryptodendrum adhaesivum) and the
Stinging anemone, (Lebrunea danae), as well as several other anemone
species (Guo et. al. 1996, Sterrer 1986; Ruzanski & Wood).

Thor amboinensis forms
a commensal relationship
with another invertebrate, usually a shallow water sea anemone or mushroom coral. The species most often used as host in Bermuda include the carpet anemone (Stichodactyla haddoni), the stinging
anemone (Lebrunia danae) and the adhesive anemone (Cryptodendrum adhaesivum). One or
several shrimps live among the tentacles of their host, feeding on
the tentacle tissue and on the mucus-trapped planktonic particles adhering to
it. In the Bahamas, Thor
amboinensis forms part of an assemblage of symbiotic invertebrates
associated with the anemone Lebrunia danae. Each shrimp, crab and brittle star inhabits its own part of the
sea anemone and Thor amboinensis is found hidden deep among
the pseudo-tentacles (Wikipedia).

To avoid
predation, Thor amboinensis relies on host anemones to keep
them sheltered from predators. The shrimp select their host by visual
distinction and chemical cues (Van den Spiegel et. al. 1998). In one study of
crustacean symbionts in anemones in Madeira and the Canary Islands, Thor
amboinensis was the most common shrimp found (Wirtz, 1997; Ruzanski & Wood). Thor amboinensis does not commonly interact with other species;
however, it is not unusual for many Squat shrimp to congregate on a single
anemone (Khan et. al. 2004). When Thor amboinensis was kept in
an enclosed aquarium environment with other organisms, it showed no hostility
towards its own species or other aquarium dwellers. Vibrant camouflage colors
are displayed on Thor amboinensis’ body to blend in with its
environment. Squat shrimp are found typically in shallower waters with little
wave disturbance (Wirtz, 1997; Ruzanski & Wood). Thor amboinensis uses sexual reproduction to produce larvae. After
intercourse, the female shrimp holds the fertilized eggs until they are ready
to hatch before releasing them into the water column. Thor amboinensis larvae
are vulnerable, slow-growing and require ample protection during maturation. Thor
amboinensis displays sexual dimorphism with the females being
significantly larger than the males (Van den Spiegel et. al., 1998; Ruzanski & Wood).
In the wild, the diet of the Squat shrimp consists of the host anemone’s
mucus-covered tentacles and the planktonic organisms trapped upon them.
However, when kept in saltwater aquariums, they consume algae and brine shrimp
(Khan et. al 2004; Ruzanski & Wood).

The female Thor amboinensis carries
the fertilised eggs under her abdomen until they are ready to hatch. The zoea
larvae pass through several stages
and, before undergoing metamorphosis, are attracted by both chemical
cues in the water and visual cues which cause them to settle near potential
host anemones. Researchers found that the larvae of Thor amboinensis were
generalists, being attracted by and accepting several different species of
anemone as hosts. In some experiments they had a preference for the species of
anemone from which the parent shrimp had been collected (Wikipedia).

Distribution

Though it is named for Ambon or Amboyna Island,
one of the Maluku Islands in
Indonesia, Thor amboinensis has a pan-tropical distribution being
found in the Red Sea, the Indian Ocean, the Pacific Ocean, the Caribbean Sea,
the Gulf of Mexico, Madeira and the Canary Islands (Wikipedia).

Aquaria

Thor amboinensis is
a popular species for marine aquaria. Sexy shrimp are often kept in
groups of three or more, due to their small size, a quality that also makes
them popular nano reef inhabitants.
They will readily host in any anemones present in the aquarium and if an
anemone is not available, may host in certain types of coral. Sexy shrimp will
scavenge for meaty food scraps, like mysis shrimp, clam, and other prepared
fish foods. If a host cnidarian is present, they may feed on the host's mucous
(Wikipedia).

Recent
ResearchResearch by Khan et. al. (2004) using
three shrimp: the Holthuis cleaner shrimp, Periclimenes holthuisi, Periclimenes
brevicarpalis (no common name) and Thor amboinensis to display
the spatial distribution of symbiotic shrimps on the sea anemone, Stichodactyla
haddoni. It was found that all the shrimp highly depended on the anemones
for shelter and food and preferred the outer tentacles of their hosts (Khan et.
al. 2004). This preference could be due to the increase in food availability
(Khan et. al. 2004). This information is important to know about the shrimp in
order for them to survive if their host is lost (Ruzanski & Wood).
In order to determine what type of anemones Thor amboinensis selects
for its hosts, Guo (1996) performed an experiment on host selection using
symbiotic shrimp and anemones. The data revealed that Thor amboinensis exhibited
no specific preference in anemones, however, it was inferred that the shrimp
were able to chemically and visually select their host (Guo 1996). Many shrimp
displayed a chemical reaction to an anemone of a particular species (Guo 1996).
This result was inferred because none of the shrimp in the experiment were able
to locate their host anemone with vision alone, but all of the specimens were
able to locate their host with both visual and chemical cues (Guo 1996). Many
shrimp also displayed a chemical attraction to an anemone of a particular
species (Guo 1996; Ruzanski & Wood).
Wirtz (1997) researched crustacean symbionts of the sea anemone Telmatactis
cricoides in Madeira and the Canary islands. Thor amboinensis was
the crustacean symbiont found most frequently in all the tested anemones (Wirtz
1997; Ruzanski &
Wood).
Increasing interest in maintaining salt water tanks has heightened the demand
for collectable aquarium fish and invertebrates (Calado et. al. 2006). A
recirculation system on shrimp breeding was studied by Calado et. al. (2006) to
improve the aquaculture of Thor amboinensis and other marine decapods (Ruzanski & Wood).

Commercial
ImportanceThor amboinensis is popularly sold around the world for use
in personal aquariums because of its beauty, abundance, and easy maintenance
(Calado et. al 2006). The Squat shrimp is considered one of the most heavily
collected marine ornamental decapods (Calado et. al. 2006). Because of its
popularity, it is important to ensure that this species is not over-collected (Ruzanski & Wood).